JPS6314346A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To prevent the deterioration in magnetic characteristics and error rate for a long period of time by disposing mixed intermediate layers consisting of a mixture of materials consisting 1st and 2nd intermediate layers between said 1st intermediate layers and the 2nd intermediate layers. CONSTITUTION:The mixed intermediate layers 15a, 15b provided between the 1st intermediate layers 13a, 13b and the 2nd intermediate layers 14a, 14b consist of the mixture of the materials consisting the 1st and 2nd intermediate layers. The mixed intermediate layers 15a, 15b consisting of the mixture of the materials consisting the 1st intermediate layers 13a, 13b and the 2nd intermediate layers 14a, 14b may be formed simply by starting the operation to form the 2nd intermediate layers 14a, 14b just before the end of the operation to form the 1st intermediate layers 13a, 13b and ending the operation to form the 1st intermediate layers 13a, 13b after the lapse of the desired time. The change of the magnetic characteristics and error rate is thereby decreased for a long period of time.

Description

[Detailed Description of the Invention] Industrial Field of Application] The present invention is a method for recording information using light such as a laser beam (the light here refers to energy rays of various wavelengths including the above-mentioned laser beam). -Relates to a method of manufacturing an optical magnetic recording medium that performs playback, erasure, etc.

[Prior Art] In recent years, research and development of optical memory elements using laser light as high-density, large-capacity memories have been carried out at a rapid pace. Among these, magneto-optical recording has attracted attention as a rewritable recording method, and the optical magnetic recording medium used for this recording is highly anticipated as a rewritable optical memory element.

Conventionally, MnB has been used as a material constituting the magneto-optical recording layer of an optical-magnetic recording medium used for such magneto-optical recording.
Typical examples are i-based, garnet-based, rare earth-transition metal amorphous-based, and the like. MnB i
The disadvantage of the garnet type is that it requires a high-power laser for recording due to its high Curie temperature, and that reproduction with a high S/N ratio cannot be achieved due to the large amount of grain boundary noise. Because of its high transmittance, it had the disadvantage of requiring a high-power laser for recording. Among them, the rare earth-transition metal amorphous system has a low Curie temperature and relatively low light transmittance, so
It is expected that it will compensate for the shortcomings of both.

This type of technology will be described in more detail below with reference to the drawings.

FIG. 3(A) is a schematic cross-sectional view of a typical conventionally used optical magnetic recording medium.

In FIG. 3(A), 31 is a transparent base material made of plastic such as polymethyl methacrylate (PMMA), polycarbonate (PC), or glass,
Generally, a plate-like substrate having a variety of shapes such as a donut shape is used. 33 is an intermediate layer made of 5iO1Si02, AIN, ZnS, etc. 32 is a magneto-optical recording layer, and for the reasons mentioned above, it is currently made of, for example, TbFe, GdT.
Rare earth-transition metal amorphous systems such as bFe and TbFeCo are widely used. 34 is a protective layer for preventing oxidation of the magneto-optical recording layer 32, and is made of an inorganic material such as an oxide or a sulfide, or a metal material.

Recording, reproducing, and erasing on such an optical magnetic recording medium is generally performed as follows.

First, the recording medium is magnetized in a certain direction perpendicular to the substrate 31, and then a spot of laser light is irradiated from the substrate 31 side. The magnetization direction may be any desired direction as long as it is constant. When the laser beam irradiated onto the substrate 31 passes through the substrate 31 and the intermediate layer 33 and reaches the magneto-optical recording layer 32, absorption of the light occurs in the laser beam irradiated portion of the magneto-optical recording layer 32, causing local damage. Temperature rises. As a result, only this portion reaches one or more Curie points of the layer-constituting material, and the magnetization disappears.

At this time, when a magnetic field is applied in the direction opposite to the in-plane magnetization direction to the part of the magneto-optical recording layer 32 where the magnetization has disappeared, the magnetization of the part is reversed, and the magnetization direction is different from that of the part not irradiated with the laser beam. Magnetic domains are formed there, and information is recorded. Erasing a record is achieved by re-irradiating the recorded portion of the magneto-optical recording layer 32 with a laser beam to raise the temperature of the portion above the Curie point, and applying magnetization in the opposite direction to that during recording. This is done by returning the magnetization direction to the state before the start of recording. In such recording and erasing, an intermediate layer 33 is provided as shown in the figure, and the thickness of the layer is set to a thickness that exhibits an antireflection function for the wavelength of the laser beam used. The temperature rise of the magneto-optical recording layer 32 can be made extremely effective for recording and erasing.

In addition, for reproduction of recording, a laser beam whose power is lowered to such an extent that the temperature of the magneto-optical recording layer 32 does not rise above one Curie point is irradiated from the base material 31 side, and the direction of magnetization of the recorded portion is changed using the magnetic Kerr effect. This is done by reading.

In order to improve the recording sensitivity of the optical magnetic recording medium as mentioned above, for example, by using an organic resin with relatively low thermal conductivity as the base material, it is possible to prevent the diffusion of the heat necessary for recording, and to improve the recording sensitivity of the optical magnetic recording medium. Attempts have been made to improve the recording sensitivity by increasing the effective temperature of the layer, or by thinning the magneto-optical recording layer 32 and further providing a reflective layer 35 as shown in FIG. 3(B). Various attempts have been made to increase the apparent Kerr rotation angle by utilizing the magnetic Faraday effect.

[Problems to be solved by the invention] However, in such optical magnetic recording, the magneto-optical recording layer is easily affected by the base material in terms of oxidation, corrosion, etc., and in particular when organic resin is used as the base material, When using magneto-optical recording layers, oxygen, moisture, etc. adsorbed on the base material may be taken into the magneto-optical recording layer during formation of the magneto-optical recording layer, resulting in deterioration of magnetic properties. In addition, if the formed optical magnetic recording medium is stored in a high temperature and high humidity atmosphere for a long time, the magnetic properties will deteriorate due to oxygen and moisture penetrating the base material and entering the magneto-optical recording layer. There have been problems such as an increase in errors during recording and reproduction and a deterioration in signal quality.

Therefore, in order to solve these problems and obtain an optical-magnetic recording medium with excellent recording sensitivity and storage environment characteristics, it is necessary to improve the relationship between the magneto-optical recording layer and the substrate in order to reduce the influence on the magneto-optical recording layer of the substrate. It is necessary that the intermediate layer provided between the two be of high quality. However, it cannot be said that this demand has always been met in the past.

In addition, when the intermediate layer has an anti-reflection structure or a multilayer film to more effectively prevent the intrusion of oxygen and moisture from the outside, it is possible to create a thin layer due to differences in the coefficient of thermal expansion of winter clothing and differences in the stress of the film. There were problems such as cracking and peeling of the thin film.

The present invention has been made to eliminate the above problems,
The main purpose is to provide an optical magnetic recording medium that has little change in magnetic properties and error rate over a long period of time, and also improves the adhesion of the thin film that makes up the intermediate layer and prevents the occurrence of cracks. be.

Means for Solving Problem C] The above object of the present invention is to provide a magneto-optical recording layer, a first intermediate layer made of a dielectric provided in contact with at least one surface of the magneto-optical recording layer, In an optical magnetic recording medium having a second intermediate layer made of a dielectric material provided in contact with the intermediate layer on a substrate, both of these layers are constituted between the first intermediate layer and the second intermediate layer. This is achieved by disposing a mixed interlayer consisting of a mixture of materials.

[Embodiments of the invention] Hereinafter, the present invention will be described in detail with reference to the drawings.

A schematic cross section of one embodiment of the optical magnetic recording medium of the present invention is shown in FIG.

In the optical magnetic recording medium shown in FIG. 1, 11 is glass;
It is made of various materials such as PMMA and polycarbonate.

The base material is transparent to the light used. Its shape is not particularly limited, and may be any desired shape, such as a disk shape.

12 is a magneto-optical recording layer, the material of which is TbFe.
, GdTbFe, TbFeCo, GdTbFeC
A rare earth-transition metal amorphous system such as o is preferably used. Of course, the above-mentioned MnBi type, garnet type, etc. can also be used.

X3a and 13b are first intermediate layers, and 14a and 14b are second intermediate layers. Each intermediate layer is made of, for example, oxide, nitride,
It consists of one or more dielectric materials such as sulfide and carbide, each of which is composed of different materials. As an oxide, 5iO1Si
02, ZrO2, MgO, etc., and ZnS as a sulfide
, B1043, etc., +lN as a nitride.

Examples of the carbide include Si3N4, ZrN, CrN, etc., and 5iC1TiC.

+5a and 15b indicate a mixed intermediate layer provided between the first intermediate layer and the second intermediate layer. Mixed intermediate layer 15a, 15
b consists of a mixture of materials constituting the first and second intermediate layers. These mixed intermediate layers can be formed using a vapor deposition method, a CVD method, a sputtering method, an ion-blating method, etc., which can simultaneously form two layers. Specifically, the operation for forming the second intermediate layer is started immediately before the operation for forming the first intermediate layer is completed (or the operation for forming the first intermediate layer is started immediately before the operation for forming the second intermediate layer is completed). A mixed intermediate layer consisting of a mixture of the materials constituting the first intermediate layer and the second intermediate layer may be formed by starting the operation) and terminating the operation of forming the first intermediate layer after a desired time. In terms of heat capacity (recording sensitivity) and film quality of the intermediate layer,
The thickness of the first intermediate layer is preferably about 100 to 3,000 layers, and the thickness of the second intermediate layer is also preferably about 100 to 3,000 layers. Further, the mixed intermediate layer provided between the first intermediate layer and the second intermediate layer and consisting of a mixture of both layers is IOλ~
The film thickness is about 1000 people, preferably about 50 to 300 people.

For the first intermediate layer, a dense film-like dielectric material made of oxide can preferably be used. Preferably, the first intermediate layer material is ZnS or SiC.
, AIN, SiN, SiO, lAg as the second intermediate layer material
0°AIN, SiN, and SiC can be used.

When the intermediate layer is made of two layers, cracks and film peeling at the interface between the two layers tend to occur due to the difference in thermal expansion coefficient and stress difference between the two layers. By providing a mixed intermediate layer consisting of a mixture of these two layers between
The above drawbacks can be solved.

The present invention is applicable not only to the above embodiment but also to various embodiments of optical magnetic recording media. FIG. 2 shows another embodiment of an optical magnetic recording medium that utilizes the Kerr effect and Faraday effect for reproduction.

22 is an optical magnetic layer. The film thickness is 100-30
08 or so is preferable. 23a and 23b are first intermediate layers;
4a and 24b are second intermediate layers, and 25a and 25b are mixed intermediate layers.

26 is a reflective layer made of ^u, Ag, Cu, AI, or the like. As explained in the prior art section, this reflective layer plays the role of increasing the apparent Kerr rotation angle by utilizing the magnetic Faraday effect and improving the reproduction efficiency.

27 is a protective layer for preventing oxidation of the magneto-optical recording layer, and is made of an organic polymer film, or an oxide, sulfide, nitride, etc.
It is composed of inorganic materials such as carbides and metal materials.

〔Example〕

Hereinafter, the present invention will be explained in more detail based on Examples.

Example 1 An optical magnetic recording medium similar to that illustrated in FIG. 1 was produced as follows. Disc-shaped polycarbonate substrate ll
On top of the film, a SiO thin film was deposited at a thickness of 100 mm (100 mm) per minute.
Film formation by sputtering was continued at a speed of 80 people/min), and after 8 minutes, ZnS sputtering was started at a film formation rate of 80 people/min, and binary simultaneous sputtering of SiO and ZnS was performed for 1 minute. After that, SiO
After finishing sputtering, ZnS was sputtered for 3 minutes to form a SiO film (second intermediate layer 14a, 1154 thickness = 800 layers), SiO and Zn.
A mixed intermediate layer 15a of S (150 people), and a ZnS film (
A first intermediate layer 12a (240 people) was formed. On top of this, the magneto-optical recording layer 12 is made of TbFeC with a film thickness of 1000 nm.
o A thin film was formed by sputtering method. Furthermore, on top of that, a ZQS film (first intermediate layer 13b, 400 layers), In
s and SiO mixed intermediate layer 15b (200 people) and Si
An O film (second intermediate layer 14b, 3000 layers) was formed in the same manner as above to obtain the optical magnetic recording medium of this example.

Comparative Example 1 First intermediate layer 1: Ia, 13b, 300 people, 5 people, respectively
A conventional optical magnetic recording medium having the same structure as Example 1 was used except that the second intermediate layers +4a and 14b were made of 900 and 3100 SiO thin films, respectively, and no mixed intermediate layer was provided. Created.

(Evaluation of the magneto-optical recording media of Example 1 and Comparative Example 1) Each recording medium was left in an atmosphere with a temperature of 60° C. and a relative humidity of 90% RH, and a storage test was conducted. Coercive force Hco before leaving,
The coercive force Hc after being left for 500 hours was measured, and the ratio of the coercive force after being left to that before being left was Hc/Hc.

The preservability was evaluated by determining the ratio (the larger the ratio, the better the preservability). The measurement results are shown in Table 1.

As shown in Table 1, Hc/Hco was 0.90 (Example 1) and 0.80 (Comparative Example 1). still,
Even after being left for 500 hours, no changes in appearance such as cracks were observed in the recording medium of Example 1 when observed with an optical microscope. In Comparative Example 1, it was confirmed that cracks were generated.

Example 2 An optical magnetic recording medium similar to that illustrated in FIG. 2 was produced as follows.

On a disk-shaped polycarbonate substrate 21, a SiO film (900 layers), 7 layers of SiO and ZnS are formed as a second intermediate layer 24a, an intermediate mixed layer 25a, and a first intermediate layer 23a, respectively.
Kunhe middle class (200 people), 7. Similarly to Example 1, 61 layers of nS films (200 people) were sequentially formed. Furthermore, a thin film of TbFe (:o) with a thickness of 160 mm was formed as a magneto-optical recording layer 22 by a sputtering method. As described above, a ZnS film (200 layers), a mixed intermediate layer of ZnS and SiO (200 layers), and an SiO film (1100 layers) were sequentially laminated in the same manner as above.A1 layer with a thickness of 800 layers was formed as a reflective layer 26 thereon. After forming a thin film by sputtering, a protective layer 27 of SiO with a thickness of 3000 nm is finally formed.
The optical magnetic recording medium of this example was obtained by forming a thin film using a sputtering method.

Comparative Example 2 The first intermediate layers 23a and 23b were each made of 300 Zn
S thin film, second intermediate layer 14a, +4b each 900
Man.

A conventional optical-electrical recording medium having the same structure as Example 2 was produced, except that the SiO thin film was made of 1,300 layers and no mixed intermediate layer was provided.

(Evaluation of the magneto-optical recording media of Example 2 and Comparative Example 2) Recording and reproduction were performed on these recording media in the same manner as in Example 1, and the C/N value and coercive force ratio (1c/Hco) were determined. The storage stability of these media was evaluated.

The results are shown in Table 1. llc/Hco is 0.90 (
Example 2) and 0.79 (Comparative Example 2). In addition, no changes in appearance such as cracks were observed in the recording medium of Example 2, but cracks were observed in the recording medium of Comparative Example 2.

Examples 3 to 6.7 to IO Various optical magnetic recording media were produced in the same manner as in Example 1, except that the configurations shown in Examples 3 to 6 in Table 1 were adopted.

Various optical recording media were produced in the same manner as in Example 2, except that the structures shown in Examples 7 to 10 in Table 1 were used.

For each recording medium of Examples 3 to IO, recording and reproduction were performed in the same manner as in Example 1, and the C/N value and coercive force ratio)
1c/1lco was determined and the storage stability of these media was evaluated. The results are shown in Table 1. No changes in appearance such as cracks were observed in each recording medium.

[Effects of the Invention] The present invention described in detail above provides an optical magnetic recording medium that exhibits little change in magnetic properties and error rate over a long period of time, and has excellent storage stability without peeling or cracking in the medium. It's now possible.

[Brief explanation of drawings]

1 and 2 are schematic sectional views showing the basic aspects of the optical recording medium of the present invention, and FIGS. 3(A)' and 3(B) respectively.
1 is a schematic cross-sectional view of a conventional optical recording medium. 11, 21.31... Substrate, 12, 22.32... Magneto-optical recording layer, 13a, 13
b, 23a, 23b・-first intermediate layer, +4a, 1
4b, 24a, 24b... second intermediate layer 33, 43
...Intermediate layer, 15a, 15b, 25a, 25b - mixed film, 2
6.35...-Reflection layer, 27.34... Protective layer. (8) (8) Fang 3 times

Claims (2)

[Claims] (1) A magneto-optical recording layer, a first intermediate layer made of a dielectric material provided in contact with at least one surface of the magneto-optical recording layer, and a second intermediate layer made of a dielectric material provided in contact with the intermediate layer. In an optical magnetic recording medium having an intermediate layer on a substrate,
An optical magnetic recording medium characterized in that a mixed intermediate layer made of a mixture of materials constituting both layers is disposed between a first intermediate layer and a second intermediate layer. (2) The optical magnetic recording medium according to claim 1, wherein a layer made of metal is laminated in contact with the second intermediate layer provided on the opposite side of the substrate as viewed from the magneto-optical recording layer.